Results of the grouper population study in the bay of Monaco: Twenty-four brown grouper counted

On the initiative of the Department of the Environment, Urban Planning and Construction (DEUC), a campaign to take an inventory of the “Epinephelus marginatus”, commonly known as the brown grouper, was carried out in the waters of the Principality in October 2006. More...The purpose of this mission was to establish a qualitative and quantitative report on the grouper population and compare it to two previous studies conducted in 1995 and 1997. The study also involved evaluating the impact of development work in Port Hercule on the population and checking whether the increase in numbers recorded on the French Mediterranean coast, was also true for Monaco. The species, of great importance from a national heritage point of view, is the most widespread of the eight species of grouper found in the Mediterranean, although it is at risk as far as its population numbers are concerned, as it is particularly vulnerable to certain types of fishing. Underwater fishing of grouper has been prohibited in the Principality since January 1993 and the species benefits from special protection measures in the French Mediterranean region, by means of a moratorium (2003–2007). From 16th to 18th October 2006, with logistics support from the Naval Services and help from divers belonging to the Prince’s Company of Carabiniers, nine biologists/divers, including seven from the « Groupe d’Etude du Mérou » (GEM), furrowed Monegasque waters, from Fontvielle to Larvotto, in order to make a census of this fish population, following a protocol that has been used for many years, especially in the reserve of the Port-Cros National Park. Divided into two teams, the divers meticulously explored the various sites, advancing 5 to 10 metres at a time and taking down the following parameters for every grouper they encountered: size, diving time, depth, characteristics of the habitat, behaviour and direction of movement. In order to prevent any duplication in the count, each team gave a report and summary of observations on the divers’ return. At the end of the campaign, Mrs Valérie Davenet, in charge of the project at the DEUC, stated: “the consensus shows a significant increase in the grouper population, which only registered 7 individuals in 1995, 12 in 1997, and today 83 specimens measuring between 20 and 110 cm. This increase is also marked by a younger population with young grouper observed (under 2 years of age), synonymous of a resurgence in reproduction, which we are absolutely delighted about”. She also pointed out that: “three years following the completion of the sea wall and counter jetty in Port Hercule, this inventory proves that the impact of the work has had no impact on the grouper population and has even contributed towards creating a favourable living environment. Furthermore, the increase in numbers, of the same order as those recorded in the rest of the French Mediterranean, is most probably the consequence of the conservation programme from which the species benefits”. The study also shows that two sectors are the most popular: the first, with 31 grouper, is located between the area below the Museum and the ball joint of the main sea wall in La Condamine Harbour, the second with 28 grouper is situated between the area below the Fairmont and the Larvotto outlet channel. A dozen fish were also counted between the jetty on the west of Fontvielle and Saint Nicolas and another dozen between the counter jetty and foot of the Fairmont. It was noted also that grouper measuring less than 30 cm were observed exclusively on the east of the Museum (ball joint, main sea wall, slope from the Spélugues and towards the Larvotto) but not in the west and that large-sized grouper are found in all sectors. Finally, an analysis of bathymetric distribution shows a high proportion of fish (56.6%) in the 20 to 30 metre deep zone, followed by 27.7% between 10 and 20 m, 7.2 % in the 0 to 10 m zone and 8.4% beyond 30m.  

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